Method for loosening threaded pipe connections using an earth drilling machine

ABSTRACT

A traveling support frame is mounted for up and down travel by two parallel guide columns secured at their lower ends to a base frame. A portion of the traveling frame projects laterally of the drive columns and supports two drive motors, two reducing gearing assemblies, a collector gearing assembly and drive head means. The traveling frame and equipment carried thereby are moved up and down by triangularly arranged thrust ram means, each comprising a downwardly opening, upwardly projecting, piston chamber having a lower mounting portion originally secured to the traveling frame and a downwardly directed piston having a lower mounting portion secured to the base frame. The drive head includes a breakout wrench having a plurality of laterally swinging wrench jaws moved in and out by linear fluid motors. The wrench jaws have radially inwardly directed wrench portions which are like spanner wrenches. The free end of each wrench jaw makes abutting contact with a shank portion of the adjacent wrench jaw, so that in use the wrench jaws brace each other and form a compression ring surrounding the engaged drill pipe. The drill head includes a tool joint component which is movable axially a limited amount relative to the traveling cross frame. A connector rod connects this tool joint component to the piston of a linear fluid motor supported axially above the drill head. Fluid is introduced into the motor below the piston for the purpose of counterbalancing the weight of the drill head and any drill pipe connected thereto. A holding wrench is located below the turning wrench. It comprises a plurality of wrench jaws pivotally mounted for lateral swinging movement, a surrounding control ring, and individual links interconnected between each wrench jaw and the control ring. The control ring is rotated by linear fluid motors. Rotation in one direction causes the links to move the wrench jaws radially inwardly into a position of engagement with holding wrench receiving portions on drill pipe, and movement in the opposite direction causes the links to move the wrench jaws radially outwardly in space relationship from the drill pipe.

United States Patent [191 Porter Apr. 9, 1974 r [54] METHOD FOR LOOSENING THREADED PIPE CONNECTIONS USING AN EARTH V DRILLING MACHINE [75] Inventor: Wilson B. Porter, Seattle, Wash.

[73] AssigneesrJamcs S. Robbins and Associates,

lasalm a i aat aanean129th of Seattle, Wash.

22 Filed: Mar. 30, 1972 21 1 Appl. No.: 239,556

Related US. Application Data [62] ,Divisionof Ser. No. 75,020, Sept. 24, 1970, Pat. No.

[52] US. Cl. 29/427 [51] Int. Cl 823p 19/02 [58] Field of Search 29/427; 173/57, 164, 152; 17 5/52, 85; 166/775 56] References Cited UNITED STATES PATENTS 3,177,944 4/1965 Knights l66/77.5

R2l,677 12/1940 Tremolada.... 3,041,901 7/1962 Knights 11/1943 Caldwell 173/57 Primary Examiner-Charles W. Lanham Assistant Examiner-James R. Duzan Attorney, Agent, or Firm-Graybeal, Barnard, Uhlir &

Hughes 51 ABSTRACT A traveling support frame is mounted for up and down travel by two parallel guide columnssecured at their lower ends to a'base frame. A portion of the traveling frame projects laterally of the drive columns and supports two drive motors, two reducing gearing assemblies, a .collector gearing assembly and drive head means. The traveling frame and equipment carried thereby are moved up and down by triangularly arranged thrust ram means, each comprising a downwardly opening, upwardly projecting, piston chamber having a lower mounting portion originally secured to the traveling frame and a downwardly directed piston having a lower mounting portion secured to the base frame. a

The drive head includes a breakout wrench having a plurality of laterally swinging wrench jaws moved in and out by linear fluid motors. The wrench jaws have radially inwardlydirected wrench portions which are like spanner wrenches. The free end of each wrench jaw makes abutting'contact with a shank portion of the adjacent wrench jaw, so that in use the wrench jaws brace each other and form a compression ring surrounding the engaged drill pipe.

The drill head includes a tool jointcomponent which A holding wrench is located below the. turning wrench. It comprises a plurality of wrench jaws pivotally mounted for lateral swinging movement, a surrounding control ring, and individual links interconnected between each wrench jaw and the control ring. The control ring is rotated by linear fluid motors. Rotation in one direction causes the links to move thewrench jaws radially inwardly into a position j of engagement with holding wrench receiving portions on drill pipe, and movement in the opposite direction causes the links to move the wrench jaws radially outwardly in space relationship from the drill pipe.

1 Claim, 13 Drawing Figures PATENTEUAPR 9 m4 SHEET 1 8F 5 50 /7&

PATENYEU APR 9 974 MET 2 BF 5 lllllllllllll lwllllll'l 1 METHOD FOR LOOSENING THREADED PIPE CONNECTIONS USING AN EARTH DRILLING MACHINE This is a division, of application Ser. No. 75 ,020, filed Sept. 24, 1970 now U.S. Pat. No. 3,695,364.

BACKGROUND OF THE INVENTION granted July 8, 1969 to Leland B. Poage, in U.S. Pat.

No. 3,490,546, granted Jan. 20, 1970 to John S. Hattrup et al., and in U.S. Pat. No. 3,463,247, granted Aug. 26, 1969 to Harold T. Klein. In other words, like each of the machines of the above-identified patents, the machine of the present invention is a precision earth drilling machine'which includes rotary drilling equipment mounted for precision movement up-and-down along a plurality of elongated base supported guide columns by traveling cross frame which is hydraulically raised and lowered. The machine of the present invention is a larger capacity machine, adapted for delivering much higher torque than any of the machines shown by theaforementioned patents.

Drilling machines of the present invention are characterized by high torque breakout apparatus for the sectional drill stem which is used with the machine, and by drilling equipmentwhich includes hydraulic means for counterbalancing the weight of the drill stem and certain components of the drilling equipment.

Known but quite different systems for decoupling threaded sections of a drill stem are shown by U.S. Pat. No. 3,181,630, granted May 4, 1965 to Robert S. Coburn; by U.S.Pat. No. 3,239,016, granted Mar. 8, 1 966 to Emmett L. Alexander; by U.S. Pat. No. 3,291,225, granted Dec. 13, 1966 to Charles D. Foran; by U.S. Pat. No. 3,446,284, granted May 27, 1969 to Normal D. Dyer and Roy L. Van Winkle; and by U.S. Pat. No.

3,460,638, granted Aug. 12,1969 to smart 0. Millsapps, Jr.

Known prior but quite different systems for hydraulically counterbalancing the weight of a drill stem are shown by U.S. Pat. No. 1,781,707, granted Nov. 18, 1930 to Waldo Sheldon, and by U.S. Pat. No. 3,151,686, granted Oct. 6, 1 964 to Archer W. Kammerer. I

SUMMARY OF THE INVENTION The drill stem weight counterbalancing equipment of thepresent invention includes-a linear fluid motor which is mounted on a frame portion of the drilling ma- According to the invention, the drill head is surrounded by a remotely controllable breakout wrench adapted to grip each section of drill pipe at a location axially inwardly of the drill pipe from its threaded connection with the drill head. The drilling equipment also includes a-holding wrench located at a wrench table spaced axially from the drill head on the drilling axis.

In use the pipe section second from the drill headlis held by this holding wrench mechanism and the drill head is rotated in reverse for breaking, i.e., loosening, the threaded joint between the first and second 1 sections of pipe. If the threaded joint between the first section of pipe and the drill head breaks first, the breakout wrench is activated to engage the first section of pipe and the drill head is again reversed for loosening the threaded connection between the first two sections. In addition to counterbalancing the weight of the drill stem and portions of the drilling equipment the lin- BRIEF DESCRIPTION. OF Tl-IE DRAWING In the drawing like letters and numerals referto like parts, and: I

FIG. 1 is an isometric view taken from above and lookingtowards one side and the front of a drilling machine constructed according to the presentinvention, showing the drilling apparatus in a partially raised position; I i

FIG. 2 is a view like FIG. 1, but showing the drilling apparatus in a lowered position;

FIG. 3 is a fragmentary, somewhat schematic front elevational view of breakout mechanism for the drill pipeand a fluid motor type counterbalancing syste for the drill head and drill pipe. 1

FIG. 4 is an enlarged scale view. partially in section and partially in elevationof the breakout apparatus shown by FIG. 3, with both the holding and driving wrenches in retracted positions;

FIG. 5 is a view similar to FIG. 4, but showing the FIG. 7 is a view similar'to FIGS. 4-6, but typifying a x situation wherein on reverse rotation of the drill head, for random breaking of the threaded joints, the lower threaded joint breaks first, such view showing the lower joint completely coupled;

FIG. 8 is an enlarged scale elevational view, with some parts in section, of the counterbalancing fluid motor and an internal parts position indicating mechanism associated therewith;

FIG. 9 is a cross-sectional view taken through the drill head above the turning wrench, substantially along line 9-9 of FIG. 3;

FIG. 10 is a cross-sectional view taken through the machine immediately above the holding wrench, substantially at the level indicated by line 10-10 in FIG. 3;

FIG. 11 is a view partially in elevation and partially in longitudinal section of a length of drill pipe;

FIG. 12 is a cross-sectional view taken through the recesses formed in the drill pipe for receiving portions of the turning wrench jaws; and

FIG. 13 is a cross-sectional view taken through the holding wrench flats, substantially alongline l3-13 of FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring more specifically to the several figures of the drawing, the illustrated embodiment is shown to comprise a lower or base frame assembly 10 including a base plate 12 and a generally U-shaped main frame 14 upstanding from the plate 12. Frame 14 includes upstanding wall portions forming a pair of sockets 16 which occupy near corner positions on the plate 12. The lower end portions of a pair of parallel guide columns 18 are received in the sockets l6 and are rigidly secured to the base frame thereby. A fixed cross frame 20' rigidly interconnects the upper ends of the guide columns 18. The guide columns 18 support and guide a movable or traveling cross frame 22. Traveling cross frame 22 includes vertically spaced apart upper and lower guide sleeves 24, 26 which surroundingly engage the columns 18. A lower portion of the traveling cross frame 22 extends laterally from the sleeves 26 into a position over the base frame assembly 10. It includes wall means 28 forming a housing for a bearing assembly (FIG. 3). A second housing 30 extends laterally from the upper guide sleeves 24 into a position above the housing 28. Housings 28, 30, sleeves 24, 26 and the interconnecting parts of traveling cross frame 22 are structurally integrated into a single rigid frame assembly.

The upper housing 30 contains collector gearing32 having a pair of inputs 34 and a single output 36. A pair of drive motor assemblies are bolted to the housing 30, and each has an output shaft which is coupled to one of the inputs of the collector gearing. In preferred form the motor assemblies comprise an electric motor 38 and'a planetary type reduction transmission 40, such as the type shown by FIG. 7 of the aforementioned U.S. Pat. No. 3,454,114.

Thrust rams 41 are essentially identical to the thrust rams shown by the aforementioned U.S. Pat. No. 3,454,1 14. Accordingly, further details of these thrust rarns 41, including the means for supplying and ex- Traveling cross frame 22 is raised and lowered by a plurality of thrust rams 41. According to the invention, each thrust ram 41 comprises a hollow piston chamber or cylinder," designated 42, and a piston 44. In the illustrated embodiment the closed ends of the piston housings 42 are directed upwardly and the open ends are directed downwardly. Mounting sockets 46 of split form receive the lower end portions of the housings 42 and firmly secure them to the traveling cross frame 22. Pistons 44 include upwardly directed head portions (not shown) and lower end mounting portions 48 which are secured to the lower frame 10. Mounting portions 48 are received between vertical plate portions of the frame member 14 and are secured to such plate portions by mounting pins 50. I

hausting a motive fluid to and from them, will not be specifically described herein. Rather, reference is made to U.S. Pat. No. 3,454,114, the contents of which are expressly incorporated herein by this reference.

As shown by FIGS. 1, 2 and 10, the guide columns 18 and two of the thrust rams 41 are spaced apart in a quadrangular pattern, with the guide columns 18 being relatively close to corner portions of the base frame as sembly 10 on one side of such base frame 10 and the two thrust rams 41 being in the corner portions on the other side of base frame assembly 10. The third thrust ram 41 is located generally between the guide columns 18 and forms a triangular pattern with the other two thrust rams 41. The drilling axis is located substantially at the center of forces within the triangle. The upper ends of the cylinders 42 are interconnected by a generally triangular shaped traveling head frame 52.

Reference is now made to FIG. 3 of the drawing. The output member 36 of the collector gearing 32 is shown to be drivingly connected to a rotary drive housing 54 supported for rotation on the traveling cross frame 22 by upper and lower sets of combination bearings 56, 58. The expression combination bearing is used herein to mean a bearing which carries both axial and radial loads. A drive head is received in a lower portion of the rotary housing 54. A plate 62 having axial splines on its periphery is connected to the upper end of drill head 60. These mesh with corresponding internal axial splines 64 carried by the inner side wall of housing 54. The peripheral splines on plate 62 and the splines 64 serve to drivingly connect the housing 54 to the drill head 60 for rotational drive but permits the drive head 60 to travel axially a limited amount relative to the housing 54.

A support stem 66 is rigidly connected at its lower end to the drill head 60 and extends upwardly therefrom. Stem 66 includes a swivel joint at 68. The swivel joint 68 connects the upper and lower portions of the stem 66 together so that they move together axially. the portion of stem 66 below swivel joint 68 rotates with the drill head 60. The portion of the support stem 66 above swivel 68 does not rotate. A piston rod 70 rigidly connects the non-rotating portion of support stem 66 with a piston head 72. Piston head 72 is mounted for linear up and down travel within a piston housing or cylinder 74 of a linear motor 76 which is mounted on top of the traveling head frame 52. The primary function of linear motor 76 is for counterbalancing the weight of the drill head assembly and the drill stern connected thereto. However, it also plays a part in the drill stem breakout technique of the present invention, as will hereinafter be described in detail.

Drill head 60 includes a drilling fluid passageway 78 extending axially through it. This passageway 78 extends from the drill head 60 upwardly through support stem 68, the swivel coupler 68, and an upper branchpart 80 of support stem 66. The branch part 80 extends upwardly through an opening 82 in plate 54. Opening 82 is sufiicently large that the branch part 80 is free to move axially up and down during axial travel of the support stem 66.

Asbest shown by FIG. 8, a radial support arm 84 extends laterally from the piston 70 below head frame 52.

The outer end of arm 84 is connected tothe lower end of a movable core 86 mounted for axial travel within.

the tubular housing 90 of a variable voltage transformer 88. Housing 90 includes an electrical coil 92 which surrounds the path of rod 86. Change in the axial position of core 86 changes the voltage output of transformer 88. Since core 86 is structurally coupled to the drill head 60 through the piston rod 70 and the support stem 66, the change in resistance of variable voltage transformer 88 gives an indication of the internal position of the drill head 60 and the other internal components connected thereto. Variable voltage transformer 88 may be in an electrical circuit (not shown) which includes a direct read out device. In some installations a variable resistor may be used in place of the variable voltage transformer.

The lower end of drill head 60 is a tool joint compo- .nent 94 connectiblc to a complementary tool joint component 96 at the upper end of each section 98 of the drill stem, 100. In the illustrated embodiment tool joint component 94 is a threaded box and tool joint component 96is a threaded pin.

The illustrated form of drill pipe 98 is of composite form. It is shown to comprise a double box major section 102 and a double pin minor section or sub 104. At least the box type'tool joint component 106 at the lower end of section 102 has threads which complement and will engage the threads of each pin component 96. e e

As best shown by FIGS. 11-13, each length of drill pipe 98 includes a triangular pattern of axially elongated recesses 108. As shown by FIG. 12,'shouIdered portions 110 are located circumferentially between the recesses. 108.

The recesses 108 are provided for receiving wrench jaw portions of a breakout wrench. A second set of recured to and is rotatedby the extension 114. A plurality of short posts 120 project downwardly from the lower end of carrier 118. An open centered plate 122 is secured to the posts 120, such as by bolts 124. Three circumferentially spaced apart wrench jaws 126 are pivotally mounted on the carrier 118 for swinging movement radially in and out relative to the position of the drill stern 100. Each jaw 126 includes an outer end portion which is received between a pair of the posts 120. Pivot pins 128 fit through openings formed in the outer end portions of the wrench jaws 126 and the wrench jaws l 26 move relative to the pins 128. The pivot pins 128 extend between the plate 122 and the carrier 118. A linear fluid motor 130 is associated with each wrench jaw 126 for moving the same into and out from its wrenching positions. The linear motors 130 are interconnected between-connectors 132 on the wrench jaws 126, near the free ends thereof, andconnectors 134 secured to the carrier 118. Pivotal connections are provided at 136 and 138 so that extension and retraction of the pistons 140 in motors 130 will cause the wrench jaws 126 to swing laterally of the drill pipe axis between the wrenching positions depicted by solid lines in FIG. 9 and the retracted or inactive positions depicted by broken lines in FIG. 9 with respect to the upper wrench jaw 126 only.

The wrench jaws 126 are of the spanner wrench type. Each includes a radially inwardly directed recess 142 which is bounded at each of its circumferential ends by a generally radially extending wrench surface, desig nated 144, 146 in FIG. 9.

When the wrench jaws 126 are in their operative positions the shouldered portions 1 10 of the drill pipe are received in the recesses 142. i

. Each wrench jaw 126 has an inner shank portion 148 which is in tight load transferring engagement with an end surface 150 of an enjoining. wrench jaw 126.

In FIG. 9 the turning wrench 116 is shown in the process of being rotated counterclockwise. The wrench surfaces 146 engage radial surfaces on the wrench sections 110. The loading on the wrench jaws 126 is such that the wrench jaws want to swing further inwardly. This means that compressive loads are transferred from each wrench jaw 126 to the next where contact ismade at surfaces 148, 150; the wrench jaws 126 are mutually self-bracing. Together the wrench jaws 126 cooperate to define a compression ring which surrounds the engaged portion of the drill pipe.

Referring now to FIGS. 1, 3-7 and 10, the base member 12 carries a holding wrench assembly 152 in axial alignment 'with'the turning wrench 116. An opening 154 is provided in table 12 in axial alignment with the opening 156 in turning wrench plate 122. Three wrench jaws 158 are pivotally connected to the table 12 by pivot pins 160. Wrench surfaces 162 are formed on radial inner portions of the wrench jaws 158. In the I illustrated embodiment the surfaces 162 are essentially flat surfaces and when the wrench 152 isin its operative position the surfaces162 form a triangular pattern which corresponds to thetriangula'r pattern of the pipe surfaces 112. In this operative position the wrench jaw surfaces 162 are contiguous the pipe surfacesll2.

The wrench jaws 158 are surrounded by a control ring 164. The ring 164 includes three radially. inwardly extending enlarged portions 166 in which are formed recesses 168 for receiving the rounded end portions of control links 170. Similar recesses 172 are formed in radial outer portions of the wrench jaws 158 to receive the opposite rounded ends of the control links 170. The guide means for the control ring 164 includes three braceblocks 174. These brace blocks 174 arecircumferentially spaced equal distances apart and are located such that when the turning wrench 152 is in its opera? tive positionthey are radially aligned with the control links and with the mating pairsof wrench surfaces 162, 112. In such operative position the control links 170 are substantially radially oriented. i

A pair of linear fluid motors 176 are interconnected between the table 12 and thecontrol ring 170. Pivotal connections 178, 180 are provided at the opposite ends of the motors 176 so that there is freedom of movement of the motors 176 as the control ring 164 turns In operation, the motors 176 are operated in unison to rotate the ring 164. In FIG. 10 the left side motor 176 is extended, the right side motor 176 is retracted,

and the wrench jaws 158 are swung inwardly into holding engagement with the drill pipe. The control links 170 areradially disposedso that the radially outwardly directed forces imposed on them by the drill pipe 100 through the wrench jaws 158 is transmitted by the control links 170 to the brace blocks 174 which are rigidly secured to the table 12. Thus, the control ring 164 does not have to by itself carry the loads imposed on the wrench jaws 158 during the breakout or joint loosening operation.

The breakout technique will now be described:

Let it be assumed in the drilling operation depicted by FIGS. 47 that the traveling frame 22 and the drilling head 60 carried thereby are in the process of being moved upwardly along the guide columns 18, and the drill stern 100 is being withdrawn from the drill hole. When the upper or first section 98 is wholly above the wrench table 12 and the holding wrench receiving depressions 112 of the second section 98 are in position at the wrench table 12 to receive the holding wrench jaws 158, axial movement of the traveling frame 22 is stopped (FIG. 4). The control ring 164 is then rotated to place it in the position shown by FIG. 10, with the wrench jaws 158 engaging the recesses 112. The portion of the drill stem 100 below the first section 98 is then restrained or anchored against both rotational and downward axial or gravitational movement.

The drill head 60 is then reversed, i.e., rotated in a tool joint loosening direction, for the purpose of randomly loosening one of the tool joints at the opposite ends of the upper section 98. The threaded connection between the major and minor parts 102, 104 of the composite section 98 are secured against separation by an epoxy bonding agent or by a different thread design. FIG. 5 relates to the situation when the upper tool joint loosens first. For the sake of clearer illustration, in FIG. 5 the upper section 98 is shown to be physically separated from the drill head 60. However, in the breakout operation the tool joint components 94, 96 are not completed separated, but rather the joint is merely loosened.

Assuming that the randomly loosening operation caused the upper joint to loosen first, and the threaded joint between components 94, 96 is not totally separated but is merely maintained loosely joined, the fluid motors 130 are operated to move the turning wrench jaws 126 into engagement with the shouldered portions 110 between the recesses 108 (FIG. 9). After this has been done the drill head 60 is again rotated in the thread loosening direction. The portion of the drill stem 100 below the upper section 98 is still retained by the holding wrench 152. During such rotation the wrench jaws 126 transmit torque from the drill head 60 to the upper section 98, resulting in a loosening of the threads at the lower tool joint 106, 96. With the tool joints at both ends of the upper section 98 now loosened, the upper section 98 can be easily unscrewed and removed from the drill stem 100. After this is done the drill head 60 is lowered and coupled to the next pipe section by loosely screwing together its box component 94 and the upstanding pin 96 of the next section 98. The drill head 60 is then raised, with the weight of the drill stem 100 being carried by the loosely engaged threads of the loosely made-up tool joint, until such next section is in a position for removal wholly above the holding wrench table 12, and the holding wrench receiving depressions 112 of the following section 98 are at the holding wrench station of the table 12. The breakout wrench 116 is again operated to engage the new upper section 98, and the drill head 60 is rotated in reverse as before to loosen the threaded tool joint at the wrench table 12. This sequence of steps is repeated with the subsequent sections until all sections of the drill stern 100 have been removed from the drill hole.

During loosening of a threaded tool joint allowance must be made for thread travel. Otherwise, thread damage will occur. According to the invention, sufficient fluid pressure is maintained in the counterbalancing linear motor 76 below the piston head 72 to bias the drill head 60 upwardly. Thus, the drill head 60 and the drill pipe 98 connected thereto progressively moves upwardly as decoupling at joint 106, 96 proceeds.

The recesses 108 are axially elongated and the turning wrench jaws 126 are positioned therein such that there is always axial clearance above and below the wrench jaws 126. This is important because the weight of the drill stem 100 must be carried by the linear motor 76 and none of it by the wrench jaws 126.

If during the initial reversal of the drill head 60, to cause a random loosening of the tool joints, the lower joint loosened first, then an added stage must be added to the technique in order to effect loosening of the tool joint between the upper section 98 and the drill head 60. This stage (not shown) involves maintaining the loosened lower tool joint components coupled, so that their threads may carry the weight of the drill stem 100, then retracting the holding wrench jaws 158, and then lowering the drill head 60, with the drill stem 100 attached, downwardly until the holding wrench receiving depressions 1 12 of the upper section 98 are at the holding wrench station of table 12. The holding wrench jaws 158 are then moved inwardly and used to support the drill stern 100 and prevent its rotation. The drill head 60 is then rotated in the joint loosening direction until the threaded tool joint 94, 96 is loosened. When this happens the joint components are maintained loosely coupled so that the threads can carry the weight of the drill stem 100. The drive head 60 is then raised to locate the upper pipe section 98 in a proper position for removal. The holding wrench 152 is reinserted on the second pipe section 98 and the first section 98, now having both of its tool joints loosened, is easily unscrewed from the second section 98 and from the drill head 60, and is then removed from the drill stem 100.

What is claimed is: 1. A method of loosening a threaded connection between first and second drill pipe sections, the first of which is thread connected to a threaded tool joint component carried by a rotatable drive head which during drilling is both rotated and moved axially, and the second of which is thread connected to the first section, said method comprising:

substantially counterbalancing the combined weights of the drive head tool joint component and the first drill stem section connected thereto by use of a fluid motor interconnected between a frame and said drive head tool joint component; gripping the second drill pipe section and restraining it against both rotation and axial movement;

coupling the first drill pipe section to the drive head at a location on said first drill pipe section which is axially inwardly on the first drill pipe section from the tool joint between it and the drive head tool joint component;

joint component and the first drill pipe section axially relative to the drive head proper an amount sufficient for accommodating thread travel at the loosened tool joint. 7 a: 

1. A method of loosening a threaded connection between first and second drill pipe sections, the first of which is thread connected to a threaded tool joint component carried by a rotatable drive head which during drilling is both rotated and moved axially, and the second of which is thread connected to the first section, said method comprising: substantially counterbalancing the combined weights of the drive head tool joint component and the first drill stem section connected thereto by use of a fluid motor interconnected between a frame and said drive head tool joint component; gripping the second drill pipe section and restraining it against both rotation and axial movement; coupling the first drill pipe section to the drive head at a location on said first drill pipe section which is axially inwardly on the first drill pipe section from the tool joint between it and the drive head tool joint component; rotating said drive head and the first drill pipe section coupled thereto in a thread loosening direction until the tool joint between the two sections loosens; and using said fluid motor for moving the drive head tool joint component and the first drill pipe section axially relative to the drive head proper an amount sufficient for accommodating thread travel at the loosened tool joint. 